1. Field of the Invention
The present invention generally relates to an electric pressure contact or connector and is more specifically directed to an electrical pressure contact having built-in opening and closing capability, i.e., a make-or-break connector or switch.
Contacts of this type can be employed in a variety of devices, e.g., modular systems, separable single-pull switches, and so on, but is particularly adaptable for use in equipping industrial current-supply connectors.
Industrial connectors must conform to regulations defined by Publication 309-I of the International Electrotechnical Commission (I.E.C.), and particularly that portion thereof which establishes the minimum breaking capacity for each size of connector.
2. Discussion of the Prior Art
In sliding contact connectors (contacts comprising connector-pins and sockets), the contact pressure exerted is perpendicular to the movement of withdrawal of the connector-pin and acts in opposition to such movement, resulting in a breaking capacity which is virtually non-existent. In order to comply with the Commission's regulations as noted hereinabove, therefore, connectors of this type need to be locked by a switch.
In pressure-contact connectors, the contact pressure is exerted in a direction parallel to the movement of separation and assists the movement, thus requiring the provision of locking means for maintaining the desired contact pressure. It is then only necessary to add a suitable device to the locking means to ensure that the contact elements separate at a predetermined distance and speed at the moment of unlocking. In this fashion, the characteristics defined in Publication 309-I of the I.E.C. can thus be readily obtained. However, some countries, and most particularly the United States, require industrial current-supply connectors to have a contact breaking capacity which is comparable to that of a switch or, in other words, that they can achieve the performance specified for switches by Publication 408 of the I.E.C. In end-pressure contacts of the type presently in use, current-supply connectors cannot satisfy this requirement because, at the moment of unlocking and before the contact elements separate, the contact pressure, which is on the order of a few kilograms, decreases and eventually falls to zero at the moment of separation, the speed of separation additionally being limited by the inertia of the system.
Two types of pressure contacts are presently utilized:
(a) for currents which are below 250 amps, pressure contacts are provided which include a resilient contact having a movable head mounted on a spring, the resilient contact being electrically connected to a stationary stud in order to connect the conductors via a braided wire element which is co-axial with the spring; and
(b) for currents which are above 250 amps, pressure contacts are used which include a rocker-arm operating at right angles to a line of contact elements.
The present invention provides a third type of pressure contact and is capable of endowing the two above-noted pressure contacts with the breaking capacity of a switch by utilizing a rocker-arm which operates in a direction which is parallel to the line of contact elements.
In comparison with contacts which utilize a braided wire element, a system of the present type offers all of the advantages of a rocker-arm contact; specifically, these advantages include:
(a) the voltage drop of the device is guaranteed to be timely because, in contrast to braided wire element devices, variable voltage drops occur only at a contact point;
(b) the disadvantages inherent in brazing or crimping of braided wire elements are eliminated;
(c) the cross-section of the rocker-arm can be formed of a size which is at least equal to the largest conductor which it is possible to connect to the device; and
(d) movement of the rocker-arm results in a powerful self-cleaning effect for the contacts of the system.
Further, in this design, each contact becomes a single-pulse switch having quick make and break-type action which is independent of the action produced by the switch operator.